This study computationally investigates to examine the impacts of repeated loading on L-shaped spandrel beams made of reinforced concrete, which were strengthened by externally bonded carbon fiber reinforced plastic sheets. The object of the research is to evaluate the following three aspects of structural behavior: degradation of reaction forces, evolution of inertia forces, and residual performance. Ayad and Oukaili's experimental impact-loading program, which featured midspan drop-weight loading on RC spandrel beams before and after strengthening, was used to validate a comprehensive three-dimensional finite element model created in ABAQUS. A sequence of 25 impacts before and 25 impacts after CFRP application was simulated to trace impact force, reaction force, inertia force, midspan deflection, and damage progression. Because of cumulative stiffness deterioration, the peak impact force in the unstrengthened beams reduced by 45%, the reaction force decreased by 54.7–57.3%, and the inertia force increased by 237.5–1090%. The peak impact force decline was limited to 31.8% with CFRP strengthening, whereas the reaction force reduction varied from 36.9% to 39%. In comparison to the much greater amplification seen prior to strengthening, the rise in inertia forces was also much reduced, staying between 114.6 and 122.2%. Additionally, there was a 19.2–23.2% decrease in the midspan deflection at the 25th impact. After 25 impacts, CFRP-strengthened beams maintained 68.3–70% of their initial capacity, but unstrengthened beams only maintained 56.2–60.1%, according to the residual performance index (RPI), which showed a notable improvement. Concrete had saturated tensile cracking prior to strengthening, according to damage analysis, but matrix microcracking (HSNMTCRT) without fiber tensile damage (DAMAGEFT) dominated post-retrofit behavior, indicating the efficient confinement and energy-dissipating function of CFRP. These results extend the previous experimental interpretation by quantifying repeated-impact trends in reaction and inertia forces, and show that externally bonded CFRP sheets improve the service-life performance of reinforced concrete ledged beams by enhancing stiffness retention, energy dissipation, inertial stability, and damage control.
